This invention relates generally to headers for agricultural machines, such as a combine harvester and, more specifically, to improvements in the crop conveying reel provided on such headers.
Conventionally, a header for an agricultural machine comprises a cutterbar operable to cut standing crop, an auger which receives the cut crop material and normally feeds it to a central opening through which the severed crop material passes to be processed by the machine to which the header is fitted, and a rotatable reel mounted generally above the cutterbar and operable to sweep standing crop towards the cutterbar and then to transport the cut crop material over the cutterbar to the auger. The reel normally comprises a plurality of circumferentially spaced, transversely extending tine bars from which project tines along the length thereof, the tine bars being mounted on and supported from the ends of spider arms spaced along the reel for rotation about the main axis of the reel. If no other mechanism were employed, the tines of each tine bar would rotate in a fixed orientation relative to the axis of rotation during each revolution of the reel; however, it is desirable to control the movement of the tines such that they maintain a constant orientation with respect to the ground as the reel rotates, primarily to prevent the tines from carrying cut crop material over the top of the reel, as opposed to disengaging or withdrawing from the cut crop material as the latter reaches the vicinity of the auger.
To this end, the tine bars have been made rotatable about their respective own axes on the reel and have been connected at their ends by respective crank arms to second spiders which are held offset from the first spiders. In operation, the reel including the first spiders are driven about the main axis which in turn drives the second spiders around an offset axis through the intermediary of the crank arms in a manner such that the tine bars are rotated about their respective own axes in a direction opposite to that of the reel and by an equal amount, whereby the tines are maintained in a given orientation relative to the ground which is set by adjusting the position of the offset axis of the second spiders relative to the main axis of the reel.
With this conventional arrangement, the tips of the tines describe a circular path which can be positioned relative to the cutterbar by adjusting, usually through the use hydraulic cylinders, the reel in both a generally vertical direction and in a generally horizontal direction. Ideally, the reel is adjusted so that the tine path lies closely adjacent and above the cutterbar as well as closely adjacent the forward edge of the auger on the other hand. However, this ideal positioning may be adversely affected if the reel is moved forwardly and downwardly which is advantageous in order to let the tines pick up down crop forwardly of the cutterbar, i.e. crop which is no longer standing upright due to inclement weather, for example.
In Soviet Union Patent Application No. SU-A-1063315, there is disclosed a reel for a combine harvester which basically is of the same type as described above but which includes a modification whereby the second or offset spiders are moved by a crank mechanism so as to vary the tine orientation during reel rotation with a view to minimizing crop losses due to flattened or down crop not being lifted by the tines for cutting by the cutterbar. This particular modification concentrates on the problem of harvesting down crop and does not address the related problems of maintaining optimum spacing between reel and cutterbar, and of transporting cut crop to the auger.